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Some boilers hold more water than others.

Brad White_9
Brad White_9 Member Posts: 2,440
This volume issue must really be keeping you awake at night, Ross! :)

Comments

  • ralman
    ralman Member Posts: 231
    Some boilers hold more water than others.

    What is the reasoning for this?

    For comparison, my current Peerless oil fired boiler has a 1 gph firing rate, 121,000 BTU output, 105,000 IBR output with 17 gallon water capacity.

    The Burnham LE-1 I am considering is 1 gph firing rate, 117,000 BTU output, 102,000 IBR output, with a 6.1 gallon water capacity.

    The ratings are pretty close. I have searched this site and others Looking for an answer. I have been reading information on how to select and size a boiler and I haven't seen any mention from what I have read about the boiler water capacity.

    Does one boiler cost less to use than the other?

    What are the factors, prerequisites or considerations that would lead me to select one of these boilers over the other?
  • Joe Brix
    Joe Brix Member Posts: 626
    Different strokes

    Low mass oil boilers are usually steel: Burnham LE, Energy Kinetics, Larrs Max, etc. But there are cast iron low volume boilers also: Biasi and Crown Freeport. Low mass boilers are usually better in cold start applications with indirects. High mass boilers are safer to use with high mass systems that were converted gravity or large volume cast iron rad systems. Some will say it's better to use a larger water mass boiler is it will fire longer but less frequently.

    Cast iron boilers are sectional and of course will increase in water volume in the larger sizes.

    I believe in low mass boilers and would rather add a buffer tank then store all that water in the boiler adding to the stand by loss. Usually easier to fit a low mass boiler into tight places and less of a strain on your back!
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Hi Ross,

    Most boiler's castings are designed for easiest manufacturing rather than best OPERATING efficiency. It is easier to cast a boiler that holds more water than one that holds less water. Even if the boiler with more water capacity has the same AFUE as the boiler with lower water capacity, the boiler with less water capacity will burn less fuel in the real world IF THE SYSTEMS ARE DESIGNED PROPERLY, especially in the days above the design temperature.

    Ron
  • ralman
    ralman Member Posts: 231
    Honestly.

    It is. This is where I am coming from. I have paid four different heating companies to check into my perception of high fuel use. The following lists their solutions.

    Company a, who also performed the install for the previous owners. = It is what it is.

    Company b, = I don't know anything at all about piping, but I'll check the boiler to see if it is dirty.

    company c, = conducted a combustion analysis. Says 6 gallons of fuel per day isn't bad.

    Called company d and asked about downfiring boiler. They said it is possible it may work. It didn't save fuel but actually made the house more comfortable due to longer run times. Did not have any other suggestions.

    I am not learning about boiler decoupling, pumping away, pri/sec piping, buffer tanks, insulation, downfiring, removing capped off monoflo tees, and outdoor reset from the professionals I hired. I learned it from you and others who have been kind enough to share their experiences.

    I would prefer to hire someone to resolve the problem. Makes my life easier, richer; does not waste others time reading/answering my questions.

    My perception is: less water to heat saves money. If fin tube is very close to output of cast iron baseboard, but reduces system water content by 40 gallons = money savings.

    The gentleman from my previous thread about dans book stated water content has nothing to do with it.

    If thats true, why different capacity heat emitters, and boilers is what is going through my mind, keeping me awake at night.

    I do not want this to sound like a rant, or be argumentative or sound like I am debating what others are saying or I am learning here.

    That is not my intent. I just want to get some sleep.
    TerrS
  • Joe Brix
    Joe Brix Member Posts: 626
    No magic bullet

    Only thing that's gonna make yo go from 6 gal a day to 2 gal is a ton of insulation. If your house is in Alaska, you can't expect to the use same amount of oil as someone on the coast in VA. a 4000 sq ft house will use more then a 2000 sq footer.

    It hasn't been a very cold winter in N.E. but I think I'm saving at least 15% or so with my new oil system. The season is averaging 3 gal / day. But when we get those days with temps in the teens, I see usage shoot up to 5gal a day. To solve this would require ripping down all the sheet rock and properly insulating the house, something I'm not going to go through the trouble or expense to do.
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Hi Ross,

    Choosing the right size boiler is just as important as choosing the right type of boiler. For example if on the coldest day of the winter, your burner only runs for 6 hours, then the system is way too big. Buying the same size boiler that you have most likely would be the wrong thing since most boilers are oversized.

    Proper controls such as outdoor reset can partially reduce the effect of an oversized system and can be especially effective if you have more radiators or baseboard than you need.

    The amount of water in the radiators and baseboards has little effect on fuel usage, in fact higher water content in the baseboards and radiators could slightly REDUCE your fuel usage since the more even heat might allow you to lower your thermostat and still have the same comfort.

    On the other hand, more water content in the boiler is more energy that can be lost up the chimney durring off cycles and more fuel usage. If that extra water was in an insulated buffer tank, it wouldn't go up the chimney.

    In most houses, reducing infiltration can often save the most fuel for the least amount of money. The next most cost effective thing in most houses would be to increase the insulation in the attic. I would highly reccomend blown in cellulose in almost all cases.

    Ron
  • Constantin
    Constantin Member Posts: 3,796
    Hmmmm....

    High-mass vs. low mass will be a debate that will go on and on, as long as modulating boilers are not available on the oil side of the business. Once the oil burner manufacturers start releasing equipment that is comparable to the neat valves and blower systems on the gas side, low-mass boilers will be the way to go.

    Until then, a number of different strategies may or may not work best, depending on the heating system in your home. For example, a low-mass boiler might work great on a RFH emitter system even in the shoulder seasons due to the large volume of water that is stored in the system, i.e. it becomes the buffer tank. On the other hand, a low-mass boiler married to short sections of baseboard or fan coils may benefit from a buffer tank for the shoulder seasons or suffer from short cycling.

    We've used about 1/8th of a gallon per square foot since September using a high-mass (31 gallon), single-stage 140kBTU-input oil boiler (Boston vicinity). If the flue gas temps were any lower, I'd have to start drilling holes in the chamber target, so this is about as low as we can go without resorting to a condensing boiler.
  • John Ketterman
    John Ketterman Member Posts: 187


    > My perception is: less water to heat saves money.


    Perception and reality are two different things. I will assume that you don't have a scientific/technical background.

    Your boiler consumes fuel to heat the entire house; the water in the boiler is a completely trivial part of the total heat mass. And the water heats up but then cools down again, giving up the heat energy to warm the house. It doesn't steal the heat permanently.

    You have not said why you think you are using too much fuel. It is not enough to "feel" that you are using too much fuel. What is the evidence? What is the vintage and construction of your house, how well insulated is it, how big (sq ft), and you are using 6 gal on how cold a day?
  • S Ebels
    S Ebels Member Posts: 2,322
    Constantin

    What are your water and flue temps running with the Vitola?

    What's the highest water temp you've encountered during heating mode this season?

    I finally hit 160+ last week at 8* below 0 and I'm curious to see how a well insulated house such as yours affects required water temp.
  • Henry_5
    Henry_5 Member Posts: 17
    There is a huge benefit to mass and water

    The great thing about mass is that it gives off heat even when the burner is not firing. The wonderful thing about water is it's capability to hold heat.

    One pound of water will hold as much energy as 8 pounds of cast. The ultimate benefit is the limited cycling that will occur with volume and mass. Hence, the longevity of scotch marine boilers for process steam and power (another thought for another time).

    Gotta run, maybe chat more later.

    Henry Nichols
  • chapchap70_2
    chapchap70_2 Member Posts: 147
    water in piping

    "The amount of water in the radiators and baseboards has little effect on fuel usage, in fact higher water content in the baseboards and radiators could slightly REDUCE your fuel usage since the more even heat might allow you to lower your thermostat and still have the same comfort."

    If this is true, why would one boiler manufacturer go through the trouble of designing a system to purge the BTU's out of the piping and boiler after every heating cycle if the boiler only contains 2 1/2 gallons of water. Wouldn't the savings in purging the boiler water be off set by the increased fuel usage of purging the system water?
  • Constantin
    Constantin Member Posts: 3,796
    Hear Hear...

    Ms. Vitola never comes close to the temperatures in heating that she produces for the the DHW system. As we speak, the system is running a 92°F boiler supply to the 4-way, while 77°F water is returning, and it's 32°F outside. Since we're running on a 0.5 reset curve, I doubt that we'll ever come close the temperatures that the DHW system calls for.

    Flue temps I have not monitored very closely but they seem to hover around 250°F, i.e. right on the hairy edge. Since I'm running B5, I worry less about the potential side effects and still plan to insulate the flue pipe in the Utility room...
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Yes, there is a huge benefit to mass and water, but it has to be where you can use it. If it is in a boiler with the burner off, it is very likely that it will be gone up the chimney before you need it.

    In my buffer tank, about 90% of the energy is still there 24 hours later and what little is lost helps heat my basement.

    Ron Schroeder
    WD8CDH
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Hi,

    They are purging out the boiler only, not the piping to the radiators, baseboards etc. Since that particular manufacturer uses a smaller DHW storage tank than some others, even 2.5 gallons is a noticable percentage of storable heat energy. The electrical energy to purge the boiler is much less than the heat energy saved from going out the flue. The purging also helps reduce the efficiency loss of short cycling and allows near steady state efficiency with shorter burn times.

    Ron
  • Bill Jirik,
    Bill Jirik, Member Posts: 54
    Boiler fire side surface to water side surface ratio

    My experience is that many of the "low mass" boilers are more effected by the mineral deposits that can form when
    excessive make up water of poor quality is introduced into the system, this is because of the ratio of waterside to fireside surface area, for sytems with the potential for excessive makeup i.e one pipe steam along with poor water quality, boilers with larger water content are my choice for longevity.
  • chapchap70_2
    chapchap70_2 Member Posts: 147
    purging zone

    > "The amount of water in the radiators and

    > baseboards has little effect on fuel usage, in

    > fact higher water content in the baseboards and

    > radiators could slightly REDUCE your fuel usage

    > since the more even heat might allow you to lower

    > your thermostat and still have the same

    > comfort."

    >

    > If this is true, why would one

    > boiler manufacturer go through the trouble of

    > designing a system to purge the BTU's out of the

    > piping and boiler after every heating cycle if

    > the boiler only contains 2 1/2 gallons of water.

    > Wouldn't the savings in purging the boiler water

    > be off set by the increased fuel usage of purging

    > the system water?



    Hi Ron,

    The boiler needs an outlet to purge the BTU's.

    "The Digital Manager turns the boiler off and continues to circulate water in the boiler and through the last active zone until the boiler is cool."

    I cut and pasted this from the company's website I was referring to. The last zone could be any heating zone or the hot water zone.
  • chapchap70_2
    chapchap70_2 Member Posts: 147
    purging zone

    Hi Ron,

    The boiler needs an outlet to purge the BTU's.

    "The Digital Manager turns the boiler off and continues to circulate water in the boiler and through the last active zone until the boiler is cool."

    I cut and pasted this from the company's website I was referring to. The last zone could be any heating zone or the hot water zone.
  • ralman
    ralman Member Posts: 231
    Thanks to all who posted under this thread.

    Shopping for a fuel efficient car to drive to work is much easier than shopping for a fuel efficient heating system for my home.
  • joe_66
    joe_66 Member Posts: 30
    FOUR WAY?

    Why the four way with the vitola?
  • joe_66
    joe_66 Member Posts: 30


    Most boiler's castings are designed for easiest manufacturing rather than best OPERATING efficiency. It is easier to cast a boiler that holds more water than one that holds less water.What?less water less material less cost to the manufacturer.E.K. post purges to correct problems they had with extreme stacking that would lead to distorted leaking boilers.they have to get rid of the heat because they dont have enough water
  • Constantin
    Constantin Member Posts: 3,796
    To protect...

    ... not the boiler, but the RFH system. Cooking the tubes isn't cool.

    To keep things simple, I left out the DHW part of the system, which brings the boiler temp as high as 160°F. Small stubs are visible in my attachment, giving a hint of what is to the right.
  • joe_66
    joe_66 Member Posts: 30
    standby heat loss

    ron ask constantin how much heat his vitola loses they just dont
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Hi joe,

    The manufacturer doesn't have to pay for the water capacity of the boiler but they do have to pay for the inner part of the mold (where the water goes) and it's removal. The inner part of the mold is usually sand but the major cost is the removal of that part of the mold after the iron is cast. The bigger the space (Water space), the easier it is to remove the inner part of the mold.

    Ron
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    OK,

    Constantin, How long does it take for your boiler to cool off 20 degrees and how long does it take for your indirect to cool off 20 degrees?

    Ron
  • Constantin
    Constantin Member Posts: 3,796
    I have no empirical basis for an answer...

    ... other than that presumably a boiler with a flue pipe will lose more energy than a well-insulated indirect, all things being equal.

    Can such losses be minimized? Sure, hot rod recommended a motorized damper on the intake for the boiler room. That would minimize infiltration and hence trap more heat inside the house at the expense of the damper install and the added complexity to the system.

    I could also insulate the flue pipe (which I plan to) to reduce the emission of heat into the boiler room. On the other hand, the steady 65°F the room achieves is quite beneficial for combustion and oil storage alike. The flue pipe is one of the big contributors to the room, as all other emitters in there have been switched off.

    When I made my boiler purchasing decision, I was not aware of a low-mass boiler that could achieve all the things I wanted my boiler system to do. The Vitola fit our needs best and so far I have been very happy with this boiler. Besides, the Vitotronic is smart enough to run a modulating burner, should they ever become available on the US market.

    Plus, while I agree with you that a low-mass boiler combined with a buffer tank is the best solution to the single-stage oil burner conundrum from a standby-loss point of view, I am not convinced that the Vitola with its very low combustion flue gas temperatures, etc. doesn't beat out non-condensing competitors once you look at the entire energy balance, not just standby losses.

    After all, a boiler that can be kept at 90°F indefinitely is going to have lower heat loss than a boiler that has to be kept at 140°F+ as many US boilers do. Anecdotal experience here points to many "cold-start" boilers not being nearly as happy with being cold-started as their manufacturers suggest. You've seen the inside of Ms. Vitola, minimal soot, virtually no rust, etc. despite being run at very low internal tank temperatures.

    Again, I have no empirical data other than flue gas temps in the mid 200's... I wish my contractor would supply me with the results of the combustion analyzer tests, perhaps he can run one next week when he comes to put in the Pro-Tek. Cheers!
  • chapchap70_2
    chapchap70_2 Member Posts: 147
    purging otherwise the boiler leaks?

    "What?less water less material less cost to the manufacturer.E.K. post purges to correct problems they had with extreme stacking that would lead to distorted leaking boilers.they have to get rid of the heat because they dont have enough water"

    Where did you get this information???????
This discussion has been closed.